Effect of Micellar Morphology on the Temperature-Induced Structural Evolution of ABC Polypeptoid Triblock Terpolymers into Two-Compartment Hydrogel Network

Published

June 28, 2024

Author(s)

Naisheng Jiang, Tianyi Yu, Meng Zhang, Bailee Barrett, Haofeng Sun, Jun Wang, Ying Luo, Garrett Sternhagen, Sunting Xuan, Guangcui Yuan, Elizabeth Kelley, Shuo Qian, Peter Bonnesen, Kunlun Hong, Dongcui Li, Donghui Zhang

Abstract

We investigated the temperature-dependent structural evolution of thermoreversible triblock terpolypeptoid hydrogels, namely poly(N-allyl glycine)-b-poly(N-methyl glycine)-b-poly(N-decyl glycine) (AMD), using small-angle neutron scattering (SANS) with contrast matching in conjunction with X-ray scattering and cryogenic transmission electron microscopy (cryo-TEM) techniques. At room temperature, A100M101D10 triblock terpolypeptoids self-assemble into core−corona-type spherical micelles in aqueous solution. Upon heating above the critical gelation temperature (Tgel), SANS analysis revealed the formation of a two-compartment hydrogel network comprising distinct micellar cores composed of dehydrated A blocks and hydrophobic D blocks. At T ≳ Tgel, the temperature-dependent dehydration of A block further leads to the gradual rearrangement of both A and D domains, forming well-ordered micellar network at higher temperatures. For AMD polymers with either longer D block or shorter A block, such as A101M111D21 and A43M92D9, elongated nonspherical micelles with a crystalline D core were observed at T < Tgel. Although these enlarged crystalline micelles still undergo a sharp sol-to-gel transition upon heating, the higher aggregation number of chains results in the immediate association of the micelles into ordered aggregates at the initial stage, followed by a disruption of the spatial ordering as the temperature further increases. On the other hand, fiber-like structures were also observed for AMD with longer A block, such as A153M127D10, due to the crystallization of A domains. This also influences the assembly pathway of the two-compartment network. Our findings emphasize the critical impact of initial micellar morphology on the structural evolution of AMD hydrogels during the sol-to-gel transition, providing valuable insights for the rational design of thermoresponsive hydrogels with tunable network structures at the nanometer scale.

Citation

ACS Applied Materials and Interfaces

Volume

57

Issue

14

Pub Type

Journals

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DOI Link

Keywords

Block copolymer, morphology, direct immersion annealing

Citation

Jiang, N. , Yu, T. , Zhang, M. , Barrett, B. , Sun, H. , Wang, J. , Luo, Y. , Sternhagen, G. , Xuan, S. , Yuan, G. , Kelley, E. , Qian, S. , Bonnesen, P. , Hong, K. , Li, D. and Zhang, D. (2024), Effect of Micellar Morphology on the Temperature-Induced Structural Evolution of ABC Polypeptoid Triblock Terpolymers into Two-Compartment Hydrogel Network, ACS Applied Materials and Interfaces, [online], https://doi.org/10.1021/acs.macromol.4c00162 (Accessed December 26, 2024)